In recent years, researches on optical devices using photonic crystals are actively conducted. APPLIED PHYSICS LETTERS 88, 081113 (2006) discloses a technique concerning a surface emitting laser including a two-dimensional photonic crystal and a multilayer mirror.
More specifically, as illustrated in FIG. 5, a Bragg mirror 3100 comprised of Si layers 3110 and SiO2 layers 3120 alternately laminated is provided on an Si substrate 3000. A two-dimensional photonic crystal slab 3300 is provided over the Bragg mirror 3100 via a bonding layer 3200 of SiO2. The two-dimensional photonic crystal slab 3300 includes In0.53Ga0.47As, a barrier layer of InP, and a quantum well layer of InAs0.65P0.35. In this structure, the average refractive index of the slab 3300 is estimated to be about 3.2.
Air having a refractive index of 1.0 forms a two-dimensional photonic crystal slab interface on the side opposite to the substrate. The bonding layer 3200 (SiO2) having a refractive index of about 1.4 forms a two-dimensional photonic crystal slab interface on the side of the substrate.
Because air and the bonding layer 3200 which are media having refractive indices lower than that of the slab 3300 are provided on both sides of the slab in this way, light generated in the slab 3300 is confined within the slab 3300. As a result, a resonant mode (an amplification mode for laser oscillation) is realized in an inplane direction of the slab 3300. Further, because, in addition to the inplane resonant mode, there is also a radiation mode in a direction perpendicular to the inplane direction, a surface emitting laser is realized.
It is also stated that some light actually leaks from the slab 3300, and by returning light which has leaked to the side of the substrate by the Bragg mirror, a Q value is increased.